In an IP Multimedia Subsystem (IMS) network, two types of Identities (IDs) are provided to subscribers.
One of the two different types of IDs is a Private Identity (PRID) used for subscriber authentication, and the other is a Public Identity (PUID), which is a phone number used for actual communication.
In the IMS network, an association relationship of n:m may be established between PRIDs and PUIDs. That is, a plurality of PRIDs may be mapped to one PRID, and a plurality of PRIDs may be mapped to one PUID.
A subscriber may have a plurality of PRIDs, which means that one subscriber may own a plurality of MSs. The plurality of PRIDs are assigned to one PUID, allowing the subscriber to simultaneously use the plurality of MSs with one phone number.
Meanwhile, if there are three MSs using the same PUID, three PRIDs are registered in the IMS network and undergo authentication. The PRIDs are uniquely assigned to the MSs in a fixed manner, and it is impossible that one PRID is dynamically assigned to a plurality of MSs.
In the IMS network, PRIDs are provided by an IMS Subscriber Identity Module (ISIM). Because MSs undergo authentication in the IMS network using authentication keys stored in the ISIM, authentication keys for authentication are uniquely assigned to the MSs in a fixed manner, making it impossible to change the assignment of authentication keys. In addition, authentication key information may not be shared between MSs with no ISIM, and it may not be shared even between different MSs owned by the same subscriber and that use the same phone number.
Meanwhile, in the conventional IMS network, it is not possible for the service provider to limit the number of MSs owned by each subscriber, and even the IMS network has no way to limit the number of authentication keys, i.e., the number of MSs capable of making authentication request with the same phone number. For example, even though a subscriber has registered eight MSs, he or she mainly uses only three MSs for actual communication. Consequently, the IMS network may unnecessarily waste resources and database space in storing and managing information about the other five MSs.